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walterhimmel1

S40 Control Unit Communication Error

Hey, I've got a 2006 Volvo S40 with a gasoline engine throwing some nasty codes. It seems to be a control unit communication error. I'm seeing overheating, the check engine light, and coolant spills due to pressure. I suspect a bad cable or plug connection. Anyone else seen this?

Summary of the thread

A 2006 Volvo S40 was experiencing a control unit communication error, overheating, check engine light, and coolant spills. The suspected cause was a bad cable or plug connection. Suggestions included checking the CAN bus wiring harness, particularly around the ECU, and considering a workshop diagnosis for potential software glitches or control module issues. The problem was resolved by fixing a faulty connection, costing 95€.

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4 comment(s)

clara_schaefer16

I had a similar problem with my S40. Overheating and check engine light, plus coolant issues. Did you check the CAN bus wiring harness for any obvious damage? It might be a long shot, but is the car running rough?

walterhimmel1 (community.author)

CAN bus wiring, noted. Thanks! Not running rough, though. Just the overheating and coolant. Where exactly should I be looking for this CAN bus issue? Any specific control module connections that are prone to this?

clara_schaefer16

On my S40 it was around the ECU. If the engine isn't running rough, it might be a software glitch or a more serious control module problem. Honestly, with the overheating and coolant loss on top of the comm error, I'd probably take it to a workshop to get properly diagnosed. Could be more than just a dodgy wire.

walterhimmel1 (community.author)

Thanks, I appreciate the advice. Turns out it was a faulty connection as suspected. Cost me 95€ to fix. Everything is running smoothly now.

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VOLVO

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S40